But playing with the Philharmonic last weekend was the culmination of years of practice, and it showed. The concert was a stunning performance that blended the rock of Phish — a style and sound that has won the band thousands of devotees willing to drop everything to follow their shows on the road — with the powerful elegance of the country’s oldest and most famous classical orchestra.

Anastasio told Time Out New York he frequently attends Philharmonic concerts with his wife and has become a big fan. He wanted this night to be more than a pop concert, but to have his music challenge these world class musicians. “The problem with a pops concert is that, in general, the musicians in an orchestra don’t feel like they’re being challenged or respected to the level of their talent. It’s like window dressing. The goal was not to do that. I want it to be a valid night of interesting music,” he said.

The evening’s program featured Phish songs arranged by Anastasio and composer Don Hart for the orchestra. The two teamed up on a long composition called “Time Turns Elastic,” which debuted last year in front of a New York audience before being released as an album. The three-movement work combines electric-guitar, vocals and orchestra to highlight Anastasio’s ambition to create challenging pieces that speak to fans of both “Bouncing Around the Room” and Bach. In May, Anastasio performed “Time Turns Elastic” with the Baltimore Symphony Orchestra with Marin Alsop conducting.

[Listen to the third movement from the recording “Time Turns Elastic”]

Saturday’s crowd gathered on the corner of 57th Street and 7th Avenue before the show was itself an eclectic blend. There were well-dressed older patrons (who looked well-acquainted with the symphony) amongst throngs of younger fans: some wore suits, others T-shirts and jeans (and one a crazy hat). In a scene uncommon for Carnegie Hall, but often seen in parking lots outside of Phish concerts, renegade “entrepreneurs” hawked balloons to a number of attendees, presumably to inhale nitrous oxide.

Inside, a loud standing ovation welcomed the performers. Another followed the first song, “First Tube.” They settled in for a couple of acoustic numbers before plugging back in his electric for “Divided Sky,” which was greeted by another round of standing ovations.

“I wish we always got that kind of reaction to our concerts. There is nothing wrong with that and any performer who says they don’t love that is lying,” said Carter Brey, principal cellist for the New York Philharmonic. “The kind of direct communication with the audience like that, who identifies so strongly with what you are doing — it is a gift and it is rare.”

[Listen to an interview with Carter Brey]

Known for roaring solos that electrify huge venues, Anastasio never drowned out the sound of the orchestra. He appeared to be concentrating intently on playing his part, alternating the focus of his gaze on the conductor, Aher Fisch, and the ceiling, rarely surveying the crowd.

The final song before the encore was a roughly 13-minute rendering of the Phish classic, “You Enjoy Myself.” The Philharmonic playfully filled in the chorus lyrics with strings and horns. As it ended, there were a couple beats of silence in the hall before the place erupted with applause that didn’t stop until the encore began.